Improvement in steam-boiler flues



UNITED STATES PATENT V OFFICE.

CHARLES B. STILWELL, OF NEW' YORK, N. Y.

IMPROVEVMENT !N STEAM-BOILER FLUES.

Specification forming part of Letters Patent No. 147,446, dated February 10, 1874; application filed J une 28, 1873.

son, show such a boiler having tubes of thin sheet metal, braced by rings fitted looscly therein.

The first part of my invention consists in bracing a thin sheet-metal boiler-fine by inserting therein a spiral Strengthening-brace, which will prevent the collapsing of the flue, and yet can easily be removed or replaced. My invention further consists in combining a conical fiue of thin sheet metal and an internal correspondin gl y-tapered spiral brace, whereby great 'strength is obtained with the Smallest practicable quantity of material.

The accompanying drawings show one of my improved fiues, A, partially broken to show the spiral brace B within.

This brace may be made either of round wire or of strips of metal, and is simply driven into the flue; it may, however, if preferred, be riveted, soldered, or otherwise fastened therein. A detachable fastening is preferred, as by its use the brace can be removed When (lesired.

I claim as my invention- 1. The combination of a spiral strengthening-brace and a boiler-flue.

2. The combination, substantially as set forth, of a conical boiler-flue and a continuous spiral Strengthening-brace.

In testimouy whereof I have hereunto subscribed my name.

CHAS. B. STILWELL.

VVitnesses:

E. O. DAVIDSON, Jos. I. PEYTON. 

